With the never-ending increase of computing power, effectively cooling a CPU has become a technical challenge. The present temperature limit for a CPU is approximately 60° C. As the power of a CPU increases, more heat is generated; therefore, the CPU requires a higher efficiency and capacity of the heat dissipation device in order to provide an effective thermal management to the computer system. Heat dissipation can be achieved by moving the heat generated primarily at the CPU and other components such as the memory controller, memory chips, graphics processor or power chips, to a location where it can be safely discharged to the ambient air.
One type conventional heat dissipation device is passive metal heat sinks. The heat sinks are typically made of thermally conductive metal blocks that can be attached to the cover plate of a CPU for dissipating heat. The block can be fabricated to include plurality of thin fins to increase the surface area for heat dissipation. The heat sinks are only effective to dissipate heat generated up to about 90 watts. Another type of conventional heat dissipation device is heat pipes, which are only effective to dissipate heat generated up to about 130 watts. Therefore, the conventional heat dissipation devices have very limited capacities and are inadequate for cooling the high power CPU, which operates with a power of about 235 watts or higher.
At this time the computer industry in general believes that liquid cooling is the only viable solution for the immediate future. Recently, major computer manufacturers have started to release high power computers using liquid cooling devices for thermal management. For example, Dell's new top line system XPC 700 includes a refrigerated liquid cooling system. IBM has released its Power 6 Plus chip at 5.2 GHz, which operates with a power in a range of 300 to 425 watts and is expected to be supported with liquid cooling devices. However, liquid cooling devices are expensive, noisy and difficult to maintain.
In heat dissipation devices based on the phase exchange of a coolant between the liquid and gas phases, the efficiency of the heat dissipation devices depends on both the evaporator and the condenser. Traditional evaporators only have one chamber or compartment above the boiler plate. When the generated vapor exits the evaporator, it encounters the returning condensate, this causes a premature condensation of the vapor before it exits from the evaporator. On the other hand, prior to the condensate reaches the boiler plate, the condensate is already heated up by the vapor. As such, the efficiency of the evaporator is compromised.
Based on the above, it is apparent that a strong need exists in the computer industry for improved heat dissipation devices that have higher efficiency and capacity for thermal management of computer systems. Furthermore, there is also a strong need for improved heat dissipation devices in other industries, such as automobile and air conditioning.